Steerable or deflectable tip cardiovascular catheters are useful in many applications, being a marked improvement over catheters with fixed tips. They are especially useful in the field of electrophysiology for performing radio-frequency ablation of cardiac tissue to interrupt abnormal electrical pathways in the heart. Typically, ablation catheters carry one or more electrodes at their distal end. A steerable catheter assists the physician in guiding the distal end of the catheter so that the electrodes can be properly aligned with the tissue to be ablated.
There are presently several useful designs for steerable tip catheters. For example, U.S. Pat. No. RE 34,502, the disclosure of which is incorporated herein by reference, describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the elongated, tubular catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston, through the catheter body and into an off-axis lumen in the catheter tip section. The distal end of the puller wire is anchored in the tip section of the catheter. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section.
Bidirectional catheters have been designed to be deflectable in one direction by one puller wire and in the opposite direction within the same plane by a second puller wire. In such a construction, the puller wires extend into opposing off-axis lumens within the tip section of the catheter. So that the tip section can bend in both directions in the same plane, the puller wires and their associated lumens must be located along a diameter of the tip section. For ablation catheters, electrode lead wires must also be provided within the distal end. Typically, an additional lumen is used to contain the electrode lead wires. Difficulties have been encountered in designing a distal tip having a relatively small diameter, e.g., 61/2 French or less, that contains three lumens where the two puller wire lumens are contained along a diameter. This is especially true where a stainless steel braided tip construction is used and where the braid circumscribes all the lumens.